This work was supported by The Hong Kong Research Grants Council (HKU763509 and HKU7/CRF/09), The University of Hong Kong (Small Project Funding 201007176079; to W-L.L. and Y-P.C.), and The S.K. Yee Medical Research Fund 2011 (to D-Y.J. and Y-P.C.). I.O-L.N. is a Loke Yew Professor in Pathology.